Disk drives typically use heads residing on sliders to read from and write to the magnetic media. Read and write transducers residing in the head are flown at a small, controlled spacing above the magnetic medium during read and write operations. To determine the controlled spacing, it is desirable for the disk drive to detect at what point the head contacts the media, known as a touchdown event.
For example, heads typically use a thermal actuator that generates heat to control the head-media spacing. Heat generated by the thermal actuator causes local thermal expansion of the head, which locally reduces the spacing between the head and magnetic media. The thermal actuator can be driven to induce sufficient heating for contact between the head and media. Detecting the touchdown point may be performed on each drive during initial drive calibration to determine appropriate thermal actuator biasing for normal drive operation. Touchdown may also be detected during normal drive operation as well as in testing.
Conventional touchdown detection may be performed using a variety of techniques. For example, touchdown may be detected through disk slow down, readout channel noise, strain gauges, PES variations, and/or acoustic emission. Touchdown may be declared when a fly height value exceeds a fixed threshold.
Accordingly, what is needed is a system and method for providing improved touchdown detection.